Flexible abrasive wheel manufacture



A nl 10, 1962 D. s. HEDDEN ,0

FLEXIBLE ABRASIVE WHEEL MANUFACTURE Filed Dec. 14, 1959 i i l INVENTOR avia '5. a dif BY we! Jam/mm,

ATTORNEY 5 United States Patent Ofifice 3,028,709 Patented Apr. 10, 1962 3,02s,709 FLEXIBLE ABRASWE WHEEL MANUFACTURE David S. Heddeu, 207 Summit Ave, Buifalo, N.Y. Filed Dec. 14, 1959, Ser. No. 859,315 9 Qlaims. (Cl. 51193.5)

The present invention relates to the manufacture of flexible abrasive Wheels, and more particularly to a new and improved flexible abrasive wheel, as Well as a new and improved method of making the same.

A typical flexible abrasive wheel normally includes an annulus of many juxtaposed and radially extending leaves of abrasive sheet material, such leaves being uniformly distributed about the central axis of the annulus. A central hollow hub supports the annulus, a pair of annular flanges support and reinforce the opposite lateral edges of the leaves around the inner peripheral portion of the annulus, and a threaded shaft is arranged within the hub and provided with lock nuts clamping the flanges against the lateral edges of the leaves and securing the entire assembly together. In operation, the shaft is driven by any suitable means for rotating the wheel.

In recent years, considerable use has been made of these flexible abrasive wheels because they are capable of rapidly and accurately grinding and finishing a variety of metal parts or other articles having hard and irregularly shaped surfaces. Such Wheels are particularly ef fective in operation because the leaves can readily flex under the applied pressure when engaging the workpieces, and the actual grinding and polishing is done by the outer peripheral edges of the leaves which wear in such a manner as to conform with the surface being abraded. Thus, these wheels are especially adapted for the production line grinding and finishing of irregularly shaped articles such as castings or the like.

In many instances, it has been found that after a preliminary operation wherein the outer peripheral edges of the leaves are Worn to conform to the surface contour of the workpieces, a relatively large number of such workpieces may be thereafter ground or finished in a single pass. Thus, a considerable amount of time is saved in the grinding and finishing operation, resulting in a substantial reduction in the cost of producing the completed article.

It has been further found that increasing the rotation of a given sized wheel about 20% beyond normal operating speed has resulted in an unexpected increase in the effectiveness of the grinding and finishing action, as Well as unexpected increase in the operating life of the wheel. An outstanding example of such a flexible abrasive wheel is disclosed in US. Patent 2,842,902, wherein the above mentioned results are described in detail.

However, in using such flexible abrasive wheels at such high speeds of rotation and under substantial pressure against the workpieces, the chief problems to overcome are the tendency of the leaves to buckle or crack adjacent the inner edges, or overcoming this, to be literally torn away from the hub and flanges by the frictional force of engagement with the workpieces and the centrifugal force created by such extremely rapid rotation.

The above mentioned patent has successfully solved these problems by adhesively bonding the adjacent inner peripheral portions of the leaves together over an area extending radially outwardly from the inner ends of the leaves a minimum of about inch across the entire width of the leaves, to form a rigidly reinforced inner rim, and by utilizing annular flanges which are embedded in one or more annular grooves inthe lateral edges of the leaves, and which flanges extend radially beyond the aforesaid minimum bonded area by about A of an inch.

However, this type of construction is not without certain disadvantages.

One disadvantage is that the separate lat- I eral reinforcing flanges are required, thereby adding substantially to the cost of the wheel. Another disadvantage is that the lateral side portions of the aforesaid rim, together with the annular flanges, actually extend a substantial distance further out radially than the minimum radial extent of the central rim portion. This substantially reduces the amount of the leaves which can be used for the actualabrading operation. For example, an embodiment specified in the aforesaid patent utilizes leaves five inches in radial length, and the reinforcing flanges and the rim extend about one inch radially outwardly from the inner edges of the leaves adjacent their lateral edges. Since th wheel cannot be operated after the leaves are worn down to this point, at least 20% of the length of the leaves adjacent their lateral edges is not usable. As is apparent, this requires more frequent replacement of the wheels and adds considerably to operation and wheel replacement costs. Still another disadvantage is that this type of wheel construction is diflicult to balance, requiring special electronic equipment, as there is no useful available area at or adjacent the ends of the hub portion for the insertion of counterweights.

Considering now the manner in which abrasive wheels are fabricated, and particularly the wheel of the aforesaid patent, it is customary to form an elongated block of the abrasive leaves, which are arranged on their shorter edges and stacked within an elongated U-shaped fixture in face-to-back juxtaposed relationship, with the edges of the leaves which will be used to form the inner periphery of the annulus being uppermost. Following this stacking step, the exposed edges of the leaves are then temporarily secured together by means of an elongated piece of tape or other suitable attaching means, whence the stack is removed from its fixture and manipulated by hand into an annulus, the leaves at opposite ends of the stack being secured together in any suitable manner. Finally, the annulus is permanently held in shape by placing it over a circular ring temporarily embedded in each side of the annulus and pouring the resin in between the inner ends of the leaves around the entire inner peripheryof the annulus and allowing the resin to harden, or by securing the annular flanges on each Side of the annulus and then pouring resin into the same area while the annulus is rotated on a specially designed fixture, all as described in detail in the aforesaid patent. While such amethod of fabrication produces a well constructed product, it will be apparent that it involves special equipment, a relatively large number of manual steps, is time-consuming, and therefore substantially increases the cost of manufacturing the completed product.

Accordingly, it is an object of the present invention to provide a novel and improved flexible abrasive wheel, which not only possesses all of the advantages of such prior art wheels, especially the previously mentioned patented wheel, but also the following'additional advantages such as simplicity of construction and economy of manufacture in that separate reinforcing flanges are completely eliminated, greater efficiency and effectiveness in operation by virtue of the fact that the reinforced area at the inner periphery of the annulus is substantially reduced without loss of strength, thereby resulting in a substantial increase in the usable area of the abrasive leaves with consequent lower operating and wheel replacement costs, and ease of balancing in that the ends of the hub are readily available to facilitate insertion of counterweights.

Another object of this invention is to provide a novel and improved method of manufacturing a flexible abrasive wheel, which method is much simpler than prior art methods, such as those described in the aforesaid patent, in that no special equipment is required, and the number of manipulative steps are substantially reduced, some steps such as stacking, taping and manually manipulating the stacked leaves into an annulus being eliminated entirely, thereby resulting in considerable savings in labor and equipment costs in producing the completed product.

Other objects and advantages of the invention will ecorne apparent upon consideration of the following detailed description together with the accompanying illustrative drawing wherein:

FIG. 1 is a sectional view through a flexible abrasive wheel embodying the invention during its formation by the inventive process of manufacture;

FIG. 2 is a front elevational view of the wheel illustrated in FIG. 1 following its completion and mounting on a driven shaft for operation, and

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2.

Referring now to the drawing, and particularly FIGS. 2 and 3 thereof, a flexible abrasive wheel constituting a preferred embodiment of the invention is generally indicated at 10. This wheel is composed of an annulus 11 and a central hub 12 supporting the annulus, the wheel being mounted on a threaded driven shaft 13 and secured by lock nuts 14 in the usual manner.

The annulus 11 is preferably composed of many rectangular abrasive leaves 15 which are arranged in juxtaposed radially extending relationship, and are uniformly distributed around the central axis x-x of the annulus. These leaves are preferably made from woven cloth having a layer of adhesive and a plurality of abrasive particles embedded therein, the abrasive coating preferably being on one side only of each leaf and all the leaves being arranged with their abrasive sides facing in the direction of rotation as shown by the arrows. Alternatively, the leaves could be paper-backed, or the weave of the cloth material could be of various types such as duck, twill, drill, etc., and the leaves could also be abrasively coated on both sides, if desired.

Leaves 15 are provided with a plurality of preferably rectangular recesses 16 in their inner edges, a pair of axially spaced recesses 16 preferably being arranged on each side of the central radial axis RR of the wheel 10. If desired, the number of these recesses 16 could be increased for greater reinforcement. When the leaves 15 are arranged so as to form the annulus 11, the corresponding recesses 16 align to form annular radial grooves 17 of about /s inch in both width and depth. The lateral edges of the leaves 15 are provided with a pair of opposed and preferably rectangular recesses 18 which also align upon formation of the annulus 11 to form annular axial grooves 29 of about /8 inch in width and depth, with outer peripheries located about inch from the inner edges of the leaves.

The hub 12 is preferably composed of a hollow and generally cylindrical, rigid core 21, preferably made of wood, and provided with a central axial bore 22 for the reception of the usual metal or plastic bushing 23 and the driven shaft 13. The outer periphery of core 21 is preferably provided with an integral and central annular boss 24, this boss preferably being arranged on the central radial axis of leaves R-R.

A pair of generally cylindrical outer peripheral portions 25 preferably are formed on core 21 on each side of boss 24. These peripheral portions 25 are made from a suitable hardened adhesive material such as an epoxy type or polyurethane type resin, and each portion includes an integral axially extending section 26. These axially extending sections fill the spacing between core 21 and the inner edges of leaves 15 and are provided with integral annular ribs 27 which fill radial grooves 17. The peripheral portions 25 also include radially extending sections 28 which cover the end faces of the core 21. contact the lateral edges of leaves 15 and are provided with integral annular outer rims 38 which fill the axial grooves 2.0.

The most important feature of the invention lies in the use of these peripheral portions 25 together with their annular ribs 27 and rims 30 which cooperate with the radial and axial grooves 17, 20 respectively in leaves 15, this structure rigidly bonding leaves 15 to the core 21. It will immediately be noted that the outer peripheries of the axial grooves 25 and rims 30 extend radially beyond the inner edges of the leaves 15 a maximum distance of about A inch, while the maximum radial extent of the radial grooves 17 and annular ribs 27 is about A; inch.

Thus, substantially the entire abrasive surface area of the leaves may be utilized for grinding or polishing, with the exception of about inch adjacent their lateral edges and about inch in their central portions. This represents a substantial improvement over a typical prior art wheel such as described in the aforesaid patent, wherein about 1 inch of the leaves adjacent their lateral edges and at least about A inch in their central portion cannot be used for the purpose desired. As will be also apparent, the structure of the above described wheel is quite simple, provides the necessary reinforcing area at the inner edges of the leaves for rigidly bonding the leaves to the hub, and yet makes the maximum use of the abrasive area of the leaves for grinding and polishing operations. In addition, it will be evident that the ends of the hub 12 are readily available for the insertion of counterweights to facilitate balancing of the Wheel.

A typical example of a flexible abrasive wheel con structed in accordance with the teachings of the present invention is as follows. The annulus 11 of the wheel 10 has an outer diameter of 14 inches and an inner diameter of 7 inches (measured across the inner edges of the leaves 15). These leaves number 700, having a length of 3 /2 inches (measured between their inner and outer edges) and are 3 inches wide (measured between their lateral edges). The spacing between the inner edges of the leaves 15 and the periphery of the core 21 is /8 of an inch, and width and depth of each of the grooves 17, 20 are inch.

The adhesive material forming the peripheral portions 25 may be of any suitable type, but preferably a self cured epoxy resin composition consisting of the reaction product of Bis-phenol A and epichlorohydrin, having an epoxy number of approximately 192 grams per epoxide equivalent and a hydroxy number of grams per hydroxy equivalent (sold under the trade names of Bakelite ERL-2774 or Ciba 2005) accelerated with any suitable commercial polyamine such as diethylene triamine, the ratio of resin to accelerator being 8:1, a suitable pigment or dye (2-5% by weight) and a suflicient amount (55-65% by weight) of a suitable filler, such as Portland cement, to control the viscosity within a range of 45,000 to 65,000 centipoise-seconds (cp. s.). It is to be noted that, the aforesaid viscosity range of the adhesive material permits the material to be poured so that it will fill the spacing between the core 21 and the inner edges of the leaves 15, as well as the radial grooves 17 and axial grooves 20, but will not penetrate into or in between the leaves any significant distance beyond the width and depth of these radial and axial grooves. Thus, proper functioning of this structure is ensured in order to obtain maximum usage of the abrasive surface area of the leaves.

Referring now to FIG. 1 of the drawing, the novel and improved method of manufacturing the inventive abrasive wheel 10 will now be described in detail. The first phase is to form the annulus 11, by arranging the inner core 21 and an outer annular metal collar 31 in substantially concentric spaced relationship on a level supporting surface 32. In the particular embodiment illustrated, the leaves 15 are substantially wider than the axial length of the core 21. Accordingly, the core is elevated slightly above supporting surface 32 by conventional washer type shims 33, and as an aid in centering the core 21 within collar 31, the former is preferably inserted over a centering pin 34 which passes through the bushing 23 in the core and shims 33, and rests upon supporting surface 32. At the same time, a plug 35 may be inserted in the upper end of the bushing 23 and core 21 to prevent entry of the adhesive material during the pouring operation described below.

The annulus is completed by inserting the required num. ber of leaves edgewise between core 21 and collar 31 in such a manner that the outer edges of the leaves con tact the collar, their inner edges contact boss 24 on core 21, and their bottom lateral edges rest upon supporting surface 32. At this point, it will be noted that the core 21 and leaves 15 are so located relative to each other that the central radial axis R--R of the leaves passes through boss 24, and the inner edges of the leaves are concentrically spaced from the core 21 on each side of the boss. Preferably, the leaves are inserted in groups, like a pack of cards, until they are uniformly distributed around the central axis X--X of the annulus 11 and are arranged in radially extending juxtaposed relationship, with the abrasive surfaces all facing in the direction of rotation. As noted previously in describing the wheel itself, the leaves are inserted in such a manner that the radial recesses 16 in their inner edges severally align on each side of boss 24 to form the desired number of annular radial grooves 17. Likewise, the opposed recesses 18 in the lateral edges of the leaves 15 align to form the annular axial grooves 20.

The next phase of the method is the formation of hub 12, and after the insertion of plug 35 into the upper end of bushing 23, the hub is partially formed by pouring a sufficient amount of the desired hardenable adhesive material into the spacing between the core 21 and the inner edges of leaves 15 in such a manner and until the upper one of the pair of peripheral portions 25 is formed. This peripheral portion includes the integral axially extend ing section 26 which fills the aforesaid spacing and is provided with the integral annular ribs 27 which fill the upper pair of radial grooves 17. This pouring step is continued until the integral radial extending section 23 is also formed, this section covering the upper end face of core 21, contacting the upper lateral edges of leaves 15 and being provided with the integral annular rim 30 filling the upper one of the pair of axial grooves 20.

Following hardening of the upper peripheral portion 25, the plug 35 is removed, the annulus 11 and core 21 are inverted (the use of the collar 31, centering pin 34 and shims 33 no longer being necessary), and the plug 35 is then inserted into the upper inverted end of bushing 23. Next. the aforesaid pouring step is repeated to form the remaining peripheral portion 25 whereupon hardening thereof, the leaves 15 are rigidly bonded thereby to the remaining portion of the core 21 and the formation of the wheel 10 is completed.

It will now be seen that the aforedescribed method is quite simple, requires no special equipment, and substantially reduces both the labor and time required to form the wheel, by reducing the number of steps to the practical minimum, and by eliminating a number of steps required by prior art methods such as those disclosed in the aforesaid patent, viz. the steps of stacking, taping and manually manipulating the stacked leaves into an annulus. As a result, the inventive method produces considerable savings in the cost of manufacture, as well as in the cost of the completed wheel.

From the foregoing detailed description, it will be understood how the invention accomplishes its various objects. It will also be understood that the aforedescribed wheel and method of manufacture thereof merely constitute preferred embodiments of the invention, and that various changes and other embodiments of the invention may be made by those skilled in the art without departing from the spirit of the invention, the scope of which is to be determined by the appended claims.

What is claimed is:

1. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges of said leaves having alined recesses forming annular grooves of about inch in depth, and a central hub supporting said annulus, said hub including generally cylindrical means of hardened adhesive material in contact with the inner edges of said leaves, provided with integral annular ribs filling said grooves, and rigidly bonding said leaves to said hub.

2. A flexible abrasive Wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the lateral edges of said leaves having opposed alined recesses forming annular grooves with outer peripheries located about inch from the inner edges of said leaves, and a central hub supporting said annulus, said hub including generally cylindrical means of hardened adhesive material in contact with the inner edges of said leaves, provided with integral annular rims filling said grooves, and rigidly bonding said leaves to said hub.

3. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges of said leaves having axially spaced alined recesses forming annular radial grooves of about /a inch in depth, and the lateral edges of said leaves having opposed alined recesses forming annular axial grooves with outer peripheries located about A inch from the inner edges of said leaves, and a central hub supporting said annulus, said hub including generally cylindrical means of hardened adhesive material in contact with the inner edges of said leaves, provided with integral annular ribs filling said radial grooves and integral annular rims filling said axial grooves, and rigidly bonding said leaves to said hub.

4. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges of said leaves having axially spaced alined recesses forming annular radial grooves of about inch in depth, and a central hub supporting said annulus, said hub including a rigid generally cylindrical core concentrically spaced from the inner edges of said leaves, and generally cylindrical outer peripheral means of hardened adhesive material on said core and filling the spacing between said core and said inner edges, said peripheral means being provided with integral annular ribs filling said radial grooves, and rigidly bonding said leaves to said core.

5. A flexible abrasive Wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the lateral edges of said leaves having opposed alined recesses forming annular axial grooves of about /s inch in depth with outer peripheries located about A inch from the inner edges of said leaves, and a central hub supporting said annulus, said hub including a rigid generally cylindrical core concentrically spaced from said inner edges, and generally cylindrical outer peripheral means of hardened adhesive material on said core, said peripheral means including integral axially extending means filling the spacing between said core and said inner edges, and integral radially extending means provided with integral annular rims filling said axial grooves, and rigidly bonding said leaves to said core.

6. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges ofsaid leaves having axially spaced alined recesses forming annular radial grooves of about inch in depth, and the lateraledges of said leaves having opposed alined recesses forming annular axial groves of about inch in depth with outer pe- 7 v ripheries located about A inch from the inner edges of said leaves, and a central hub supporting said annulus, said hub including a rigid generally cylindrical core concentrically spaced from the inner edges of said leaves, and generally cylindrical outer peripheral means of hardened adhesive material on said core, peripheral means including integral axially extending means filling the spacing between said core and said inner edges and provided with integral annular ribs filling said radial grooves, and integral radially extending means in contact with the lateral edges of said leaves and provided with integral annular rims filling said axial grooves, and rigidly bonding said leaves to said core.

7. A flexible abrasive Wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges of said leaves having a plurality of axially spaced alined recesses forming annular radial grooves of about inch in width and depth, and a central hub supporting said annulus, said hub including a rigid generally cylindrical core provided with an annular boss in contact with the inner edges of said leaves between certain of said grooves and concentrically spacing said core from said inner edges, and a pair of generally cylindrical outer peripheral portions of hardened adhesive material on said core, said peripheral portions including integral axially extending annular sections filling the spacing between said core and said inner edges on each side of said boss, being provided with integral annular ribs filling said radial grooves on each side of said boss, and rigidly bonding said leaves to said core.

8. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves inner edges, and a pair of generally cylindrical outer peripheral portions of hardened adhesive material on said core, said peripheral portions including integral annular axially extending sections filling the spacing between said core and said inner edges, and integral radially extending sections in contact with the lateral edges of said leaves and provided with integral annular rims filling said axial grooves, and rigidly bonding said leaves to said core.

9. A flexible abrasive wheel comprising an annulus of many juxtaposed and radially extending abrasive leaves uniformly distributed around the central axis of said annulus, the inner edges of said leaves having a plurality of axially spaced recesses severally alined on each side of the central radial axis of said annulus and forming annular radial grooves of about A; inch in width and depth, and the lateral edges of said leaves having opposed alined recesses forming a pair of annular axial grooves of about /s inch in width and depth with outer peripheries located about inch from the inner edges of said leaves, and a central hub supporting said annulus, said hub including a rigid generally cylindrical core of lesser axial length than the Width of said leaves and provided with a central annular boss arranged on said radial axis in contact with the inner edges of said leaves and concentrically spacing said core from said inner edges, and a pair of generally cylindrical outer peripheral portions of hardened adhesive material on said core, said peripheral portions including integral axially extending annular sections filling the spacing between said, core and said inner edges on each side of said boss and provided with integral annular ribs filling said radial grooves, and integral radially extending sections covering the ends of said core, contacting the lateral edges of said leaves and provided with integral annular rims filling said axial grooves, and rigidly bonding said leaves to said core.

References Cited in the tile of this patent UNITED STATES PATENTS 2,749,224 Block June 5, 1956 2,796,337 Block June 18, 1957 2,818,691 Leggett Jan. 7, 1958 2,842,902 Miller et al. July 15, 1958 

